A need has been identified in recent years in terms of providing real time intra-operative refraction or wavefront measurement feedback to a surgeon performing a refractive cataract surgery or other vision correction procedures on the eye of a patient. The intra-operative refraction or wavefront measurement, especially one obtained from an aphakic eye when the natural lens of the eye is removed, can help to guide a surgeon better determine the optical power of an IOL (intra-ocular lens) (in terms of sphere power for a monofocal or multi-focal or extended depth of focus IOL or accommodating IOL, and cylinder in addition to sphere if the IOL is a toric IOL or even higher order aberration correction if it is a premium higher order correction IOL). Such an approach has been shown to produce better surgical outcomes. Meanwhile, an intra-operative pseudo-phakic refraction or wavefront measurement can also confirm if a targeted refraction has been achieved to within a certain acceptable tolerance and if not, further adjustment (such as a further rotation of an implanted toric IOL or limbal relaxing incision) can be made to finely tune the refraction.
However, one issue associated with the use of an intra-operative wavefront aberrometer or auto-refractor is that the real time refraction value can vary as a result of many dynamic surgical factors, including the alignment of the patient eye relative to the aberrometer or auto-refractor, patient fixation and angle alpha (angle between the center of the pupil and the visual axis), varying pupil size, the intra-ocular pressure (IOP), the hydration of the incision wound, the tear film, and the pressure exerted on the cornea from eye-lid-opening speculum. With proper control of these dynamic surgical factors and artificial intelligence including refraction confidence calculation to qualify and hence reject disqualified refraction/wavefront data, the variation in the measured refraction can be controlled to a certain range. However, there can still be some variation in the measured refraction when a patient eye is aligned relative to the intra-operative aberrometer or auto-refractor. This is more the case when an eye is aphakic, as an aphakic eye generally has a larger absolute base sphere refraction value simply because the wavefront from an aphakic eye is more divergent than that from an emmetropic eye. As a result, the recommended intra-ocular lens (IOL) power based on the real time aphakic refraction (combined with other biometric parameters) can also change in real time, for example, when the eye is re-aligned. This can cause some confusion to a surgeon in determining what exact IOL power to select for implantation during a cataract surgery.
In light of the above, there is a need in the art for a means to show a surgeon how repeatable a refraction reading is and/or how confident the refraction is. In the aphakic state, this will allow the surgeon to make a more informed decision in terms of selecting a recommended IOL power and in the pseudo-phakic state, this will allow the surgeon to finely tune the final position of an implanted IOL until with higher confidence.
One or more embodiments of the present disclosure satisfy one or more of the above-identified needs in the art. One embodiment is a means to present to a surgeon a histogram of real time refractions at each stage of a refractive cataract surgery, i.e. phakia, aphakia and pseudo-phakia. Another embodiment is to automatically and intra-operatively detect the phase of a cataract surgery (i.e. to intra-operatively determine if a patient eye is phakic, aphakic, or pseudo-phakic). Another embodiment is to display a real-time, dynamic histogram of a recommended IOL power calculated from aphakic refractions together with other biometric parameters of the eye.
One aspect of the present disclosure is to record the occurrence frequency of qualified and/or rounded real time refractions and to display the occurrence frequency distribution or histogram of the refraction data. This will present to the surgeon an information rich display of quantitative refraction instead of a most recently single qualified refraction at one point in time, which may be more variable. Another aspect of the present disclosure is to use phakic biometry measurement results of an eye obtained either pre-operatively or intra-operatively to estimate its aphakic refraction, to use an estimated aphakic refraction to automatically detect the aphakic phase of the eye. Still another aspect is to use intra-operative biometry measurement to determine the cataract surgical phase of an eye. Still another aspect is to use intra-operative Purkinje images to determine the cataract surgical phase of an eye. Still another aspect is to combine real time aphakic refraction with phakic and/or aphakic biometry to calculate an IOL power per a targeted final refraction and to present to a surgeon a dynamic histogram of the IOL power recommendations during the aphakic phase. Still another aspect is to optimize and personalize the IOL power calculation in a regression manner by collecting data over a relatively large number of patients for each surgeon to account for surgeon factors.
Another embodiment of the present disclosure is to display the confidence level of real time intra-operative refraction. One aspect is to calculate a confidence level or value based on an algorithm that takes into account all wavefront and/or aberrometry data qualifiers and to present to a surgeon the confidence level or value as a height or length varying percentage bar. Another aspect is to correlate the confidence percentage value to a color encoded confidence percentage indicator (such as the word “Rx”). In this case, the confidence value can be digitized such that for a certain real time refraction that falls within a certain digitized confidence value range, a certain color selected from a color spectrum is assigned to the real time refraction and is displayed to the surgeon.
Still another embodiment of the disclosure is to combine the calculation of the occurrence frequency or probability distribution of qualified refraction with the confidence level of the refraction to produce a combined confidence weighted histogram and to present this confidence weighted histogram to a surgeon in real time. One aspect is to use the confidence weighted histogram to pick the most steady aphakic refraction, and to use the chosen aphakic refraction to calculate the IOL power. Another aspect is to allow the surgeon the option to display only the refraction histogram and/or the refraction confidence bar and/or the combined confidence weighted refraction histogram to guide the surgery. In particular, at the aphakic phase, the surgeon can select the IOL power based on the live, dynamic IOL power histogram; and at the pseudo-phakic phase, the surgeon can use the live refraction histogram to rotate an implanted toric IOL or to perform a guided limbal relaxing incision.